This invention relates to apparatus for removing foreign matters in liquid, and more particularly to apparatus for removing foreign matters such as marine organisms from cooling seawater used in a condenser etc. of a cooling seawater system.
Seawater is sometimes employed as cooling water for condensers in thermal and nuclear power stations etc., and the inflow of marine organisms etc. into the cooling seawater has heretofore been prevented by means of a screen disposed at a seawater intake, and so on. However, marine organisms etc. which breed in a waterway behind the screen or a piping system are introduced into the water chamber of the condenser by a water current and block the inlet part of a cooling pipe, or they accumulate in the pipe to such an extent so as to reduce the quantity of the cooling water. Moreover, the marine or organisms or the like may even cause leakage due to the erosion and the corrosion pitting of the pipe material. It is also a cause for the frequent occurrence of the above troubles that, although chlorine had been injected into the seawater for suppressing adhesion or growth of organisms such as shells, the chlorine injection process has been stopped for the reason of such adverse influence as destroying beneficial marine organisms.
There has been known a technique wherein, in order to prevent such drawbacks, a filter is disposed in the cooling water inlet pipe of the condenser to remove foreign matters such as marine organisms from the system before the cooling water flows into the water chamber. This kind of apparatus is shown in U.S. Pat. Nos. 3,875,063, and 3,828,930 wherein a cylindrical housing and a cylindrical filter disposed coaxially therein define an annular space therebetween, and the housing is provided with a radial inlet pipe at the upper portion of the filter, and an outlet pipe arranged axially of the filter at the lower portion. By deflector means provided in the radial inlet pipe swirling fluid flow is formed around the filter. It seems that since the swirling fluid flow decreases in its velocity toward the outlet pipe and the fluid in the annular space flows into the filter, there are fluid flows carrying solids to be separated near the outlet pipe so that the filter may be clogged near the outlet pipe and a practical filtering face is reduced. In both of these apparatus it is required that, during foreign matter extracting operations, the quantity of extracted water is small; a rise in the pressure loss due to the installation of the apparatus is low; and a clogging of a strainer does not occur.
More particularly, when the foreign matters are extracted, the cooling seawater is simultaneously extracted. Therefore, decreasing the quantity of the cooling water to the minimum is necessary for maintaining the performance of a condenser. In addition, the pressure loss corresponding to a water current resistance is incurred by the installation of such apparatus in the piping system. The increase thereof results in an increase in the pumping power of the cooling water, and therefore needs to be suppressed. Further, the clogging of the filter surface due to the foreign matters needs to be avoided because such clogging results in an abnormal rise in the pressure loss.
Apparatus for removing foreign matters meeting the above requirements are desired.